The present invention relates to an improvement introduce compressors and, more particularly, to a new muffler resonance chamber construction for high frequency noises caused by compression pulses occurring inside the cylinder of a compressor of that type, usually employed in small refrigeration and air conditioning systems.
Hermetic rotary compressors with a rolling piston and/or sliding vane arc high internal pressure high side compressors wherein the refrigeration fluid compressed in the compression chamber is discharged directly inside the compressor shell. This causes the noise in this kind of compressor to be largely influenced by the compression and discharge pulses that result in a characteristic high-frequency noise. The solution usually employed to reduce the noise level in rotary compressors is to provide an intermediate muffler between the discharge from the compression chamber and the inside of the compressor shell. It happens that this solution works only to reduce the noise caused by the discharge Pulses and has no effect on the compression pulses, that is the pressure pulses in the refrigerating fluid flow which are already happening in the compression chamber inside the cylinder before the discharge. Such pulses also generate high frequency noises.
A solution addressed to solve the pressure pulses inside the compression chamber is described on U.S. Pat. No. 4,427,351. That document proposed the provision of a volume adjacent to the cylinder discharge orifice, so that this volume operates as a Helmholtz-type resonance chamber or cavity. Notwithstanding the fact that this chamber effectively attenuates the high-frequency noise, it has the drawback of increasing the cylinder dead volume, which necessarily implies a decrease in the volumetric performance of the compressor. Another drawback is that the manufacturing of the resonant chamber therein proposed is relatively difficult.